Health @ Heart

By Philip S. Chua, M.D.

Potatoes and diabetes

Eating potatoes, especially french fries, is associated with an increased risk of developing Type 2 diabetes, reported the American Journal of Clinical Nutrition in a prospective study supported by the National Institutes of Health published in its February 2006 issue.

"Potatoes, a high glycemic form of carbohydrate, are hypothesized to increase insulin resistance and risk of type 2 diabetes," according to Thomas L. Halton, M.D., and his colleagues at Harvard Medical School and Brigham and Women's Hospital in Boston, Mass.

What is Glycemic Index?

Glycemic Index is a measurement of how fast or slow the body transforms the carbohydrates we eat into glucose (blood sugar). The higher the glycemic index, the faster the food elevates the blood sugar level.

What are the types of carbohydrates?

There are two types of carbohydrates: simple and complex. Simple carbohydrates have high glycemic index, more easily and rapidly digested by the body; and complex carbohydrates have low glycemic index, and digested more slowly.

Simple carbohydrates are found in fruits (apples, all the berries, grapefruit, kiwi, lemon, pear, oranges, peach, melon, plum), and they are low in simple sugars and do not promote weight gain. Simple carbohydrates, which are high in simple sugars and cause weight gain rapidly, include: table sugars, cakes, ice cream, non-diet pop beverages, candies, chocolate, fudge, jam, honey, pudding, sweets and desserts, in general. They are easily and rapidly digested by our body.

Complex carbos are found in almost all plant-based foods. The body digest these foods more slowly, and some of these are bran, wheatgerm, corn, barely, oatmeal, buckwheat, pasta, macaroni, brown rice, potato, brown bread, cassava, yam, muesli, lentils, peas, beans. They are the "healthier complex carbohydrates." These are essential to an exercise regimen, making each workout more effective in losing body fat and weight. However, potatoes now seem to have gained this new notoriety with this recent published prospective study.

How does exercise lead to loss of fat and weight?

When we exercise for a brief period, say 30 minutes, the body turns our carbohydrate (glycogen) reserve in the body into blood glucose to provide the needed energy. If we exercise longer, or more intensely, and used up the glycogen stores, then the body metabolizes (uses and consumes) our fat reserves...so we lose fat, and become slimmer.

How large was this Harvard study?

The prospective study was initiated in 1976 and included 121,700 registered female nurses. Their diet was assed every four years from 1980 to 1998) and lifestyle and disease (which developed during this study) status were assed every two years. Thos who left more than 10 food items on the survey questionnaire, or had questionable answers regarding caloric intake, or who had cancer, cardiovascular illness, were excluded from the study. The remaining 84,555 were followed up for 20 years.

What were the findings?

This investigation showed that "4496 participants were diagnosed as having type 2 diabetes. After adjustment for age and dietary and non-dietary factors, potato and french fry consumption were both positively associated with increased risk for type 2 diabetes. Even more pronounced in the association between potato and diabetic risk was found among the obese and sedentary women in the study.

What do these findings mean?

The data from this significant study strongly suggest a potential benefit from limiting the consumption of potatoes, especially french fries, in reducing the risk of type 2 diabetes. Other studies have likewise shown that eating a lot of the Simple Carbohydrates that are HIGH in simple sugars (review list above) lead to weight gain and obesity and an increased risk of diabetes.

Carbohydrates with lower glycemic indices, such as high-fiber forms of (complex) carbohydrates like whole grains, bran, oat meal, wheat, muesli, lentils, peas, beans, broccoli, in combination with a low-fat diet of fish, green leafy vegetables and nuts, plus daily exercise reduce our risks, not only from diabetes, but from cancer and cardiovascular illness, like heart attack and stroke.